454 modifications

gaiter · 03-13-2008, 02:10 PM

I have a 96 Powerquest SX220 with a 454 (I beleive it is 300 or 310 hp). I am thinking about doing some modifications to the motor and was wondering if this is still good advice:

http://www.offshoreonly.com/forums/s...ight=454+roids

I am running 63 mph right now, would like to run a solid 70. I want the motor to be reliable, and am looking for advice as to what the best course of action is.

BY U BOY · 03-13-2008, 02:24 PM

All that info is great. Do some more searches and you will come up with enough information about diff combos to keep you reading for the next few days.

Many people have done modifications from minor to ridiculous with their 454's. If you have questions ask them as some people (i know i do ) enjoy learning new things that work with diff combos.

scarabfun · 03-14-2008, 05:59 PM

i have worked over 454's now 468's ( bored 60 over). tuff call for you. i have alot into mine . full roller motor merlin rectangle port heads, custom cams, gil dry pipes and so on. about $8000 each , maybe more. 450-500 hp. very reliable. i thought about 502 crate motors ($6000 or so) but this way i know what i have and my engine shop is very fussy. it will take you about 100 hp to get the speed you want i think. just remember nothing comes cheap & you get what you pay for...

niceguy · 03-14-2008, 07:53 PM

I have to put my two cents .... if your intent is to freshen the motor, then now is the time to go ahead on with the mods. Here is what I'd recommend (I am no expert, just a HP junkie): a good Eagle rotating assembly with 4.250 stroke with a forged assembly and flat-tops, this will make a 496ci with a .030 bore of your stock 454.

If you are not going to put boost to the motor, shoot for right around 10:1 compression. If you might add boost later, stick with around 9:1 or 9.25:1.

Get a decent size hydraulic roller something about midsized, get a decent set of marine style heads.... spend the money with a good head porter, use a 2.30 SS intake and a 1.88 or 1.90 exhaust (Inconel fo sho) make sure you have excellent mid-lift flow numbers and the most important isnt peak flow, it's average flow from .300-.650 lift. Go with a good intake, something like an RPM or torquer and say a 800cfm carb. And to make it even less expensive, re-use the heads you got, just have bigger valves and DEFINITELY have the port work done to the stock heads. Now with the ported stock heads, you'll lose probably 50hp or so.... maybe a tad more, who knows, but it would definitely be cheaper.

That should be good for an easy 450-500hp on pump gas with the good heads, without turning it stupid high rpm. Hell it might make more!!

If you just want more power.... buy a blower and be done. That is the cheapest and easiest HP in the world. And reliable as all get out.

Just my opinion.... take it for what it's worth... it's free.

scarabfun · 03-14-2008, 08:06 PM

i'm just not sure what kind of $$$ Gaiter want's to spend. i do know from experiance that 500-550hp can be done but to do it and get long life out of it is two differant thing's. i got 7 year's out of these engine's til last summer, i think that's pretty good so i went back to my builder to do it again. my builder said add a blower and cut engine life in half.

niceguy · 03-14-2008, 08:35 PM

Scarabfun.... getting that kind of power out of a 468 reliably is not a problem. Getting 650hp reliably.... now that is tougher, but could be done.

I'm not sure what kind of money he wants to spend either, but as you stated, HP is not cheap.

I am a little confused about boat power.... I have built numerous street motors for my different hotrods throughout the years. One of which was a 406 23 degree headed small block on pump gas that made 575hp. And I drove that motor for almost 2 years and I never lift and am always stomping the gas. I dont see the big problem with making a big rat make decent power on pump gas that will live.... the only thing I could see needing to do is change valve springs each season.

If you had a 468 and it only made 1.2hp/ci that it would make 561hp. My small block made 1.41 hp/ci!!!

Not trying to get in a pissing contest here.... just making a statement and in a way asking a question.

Are boat motors THAT much different than street motors?

scarabfun · 03-14-2008, 09:08 PM

i know, i'm not trying to pick a fight. running a marine engine is best described as driveing up-hill all the time, the engine is alway's under load. even drag motors get to coast.

HaxbySpeed · 03-14-2008, 10:06 PM

The edelbrock RPM marine heads are very cheap and come with inconel exhaust valves. I did the top end on a stock 330 horse 454 with the RPM oval port marine heads, air gap intake, 750 carb, Comp xm270h hydraulic flat and didn't touch the bottom end. It made 485hp and had a nice flat torque curve. it has just over 400 hours on it now without a single issue. I built another one with the same top end package, but a better rotating assembly and a slightly bigger hydraulic roller. It made 510hp

niceguy · 03-14-2008, 10:18 PM

Rock on... I hear ya on the always under a load. I think we're on the same page.

Haxbyspeed.... that sounds about right on par with what I'm saying. Were those heads you used box stock?

Love these types of discussions... I could do this all night long. LOL

HaxbySpeed · 03-14-2008, 10:32 PM

Right out of the box for both. Just checked the spring pressure and bolted em on..